1. Field of the Invention
The present invention relates to an optical lens acting on light emitted from a light-emitting device, a method of manufacturing an optical lens, and a drawing optical lens preform for making an optical lens.
2. Related Background Art
Japanese Patent Publication No. 3121614 and U.K. Patent Application GB2108483A disclose methods of manufacturing a microlens by drawing. In the methods disclosed in these literatures, a columnar preform is prepared and then is drawn upon heating, whereby a columnar lens having a cross-sectional form substantially the same as that of the preform is formed.
In such a conventional method of manufacturing an optical lens, the preform may incur distortions and the like in the process of drawing, thus deforming, whereby there have been cases where an optically active part to act on incident light is not formed as designed.
Therefore, it is an object of the present invention to provide an optical lens preform, a method of manufacturing an optical lens, and an optical lens in order to manufacture an optical lens as designed.
For achieving the above-mentioned object, the drawing optical lens preform in accordance with the present invention is a drawing optical lens preform, formed like a pillar from a translucent material, comprising a first curved face part formed by an aspheric surface in one side face and a second curved face part, formed in a side face opposite from the first curved face part, having a principal curvature smaller than that of the first curved face part. The principal curvature described in this specification refers to the curvature of a circle (columnar face) obtained when a curve (curved face) is approximated by the circle (columnar face).
In such a drawing optical lens preform, since the second curved face part is formed, distortions are restrained from occurring due to drawing as compared with cases made flat.
Also, since the curved face part is divided into first and second curved face parts whereas the first curved face part having the greater curvature is formed aspheric, distortions are less likely to occur due to drawing, whereby the aspheric surface form can be restrained from deteriorating.
Here, both of xe2x80x9caspheric surfacexe2x80x9d and xe2x80x9cspherical surfacexe2x80x9d (mentioned later) refer to forms of curved faces parallel to a pillar axis direction 80 shown in FIG. 1A, such as the first curved face part 43, e.g., individual parts constituting the outer form of a cross section taken along a surface orthogonal to the pillar axis direction. Then, xe2x80x9caspheric surfacexe2x80x9d refers to a curved form constituted by a curve having at least two curvatures. For example, it refers to a form in which the curvature of the curved part on the inner side (center part) is made greater than that in the outer side (peripheral part) in the present invention.
Preferably, the second curved face part is formed by a spherical surface. This makes it easier to form the second curved face part. Here, xe2x80x9cspherical facexe2x80x9d refers to a curved face having a single curvature.
The second curved face part may be a convex surface.
Also, the second curved face part may be a con cave surface.
The method of manufacturing an optical lens in accordance with the present invention includes a drawing optical lens preform preparing step of preparing one of the above-mentioned drawing optical lens preforms; a drawing step of drawing the drawing optical lens preform prepared by the drawing optical lens preform preparing step to a desirable outer diameter; and an optical lens preparing step of slicing the drawing optical lens preform drawn by the drawing step; wherein at least the first curved face part in the first and second curved face parts in the drawing optical lens preform drawn by the drawing step functions as an optically active part acting on incident light or outgoing light.
In such a method of manufacturing an optical lens, since the form of the optical lens, the form of the optically active part in particular, can be determined in a stage prior to the drawing, it can be processed while in a sufficiently large size.
When the second curved face part is formed so as to yield a curved face as a result of drawing, the first and second curved face parts function as an optically active part in thus prepared optical lens. When the second curved face part is formed so as to yield a flat face as a result of drawing, the first curved face part functions as an optically active part in thus prepared optical lens.
Here, xe2x80x9cacting on lightxe2x80x9d refers to an action in which incident divergent light is emitted with its angle of divergence being reduced. On the other hand, xe2x80x9cslicingxe2x80x9d encompasses cutting the drawn drawing optical lens preform and shaving it into a desirable form or size.
Preferably, in the drawing optical lens preform preparing step, the curvature of the second curved face part is determined according to a curvature for carrying out a desirable optical action and an amount of deformation occurring due to drawing. As a consequence, the curvature of the second curved face part is determined in view of the amount of deformation which may occur due to drawing, whereby the deformation upon drawing can be suppressed to minimum after the drawing.
In another aspect, the method of manufacturing an optical lens in accordance with the present invention includes a drawing step of drawing one of the above-mentioned drawing optical lens preforms to a desirable outer diameter; and an optical lens preparing step of preparing an optical lens by slicing the drawing optical lens preform drawn by the drawing step; wherein at least the first curved face part in the first and second curved face parts in the drawing optical lens preform drawn by the drawing step functions as an optically active part acting on incident light or outgoing light.
The optical lens in accordance with the present invention is made by one of the above-mentioned methods of manufacturing an optical lens.
Since the preform is processed while in a sufficiently large size whereas the provision of the second curved face part restrains the drawing optical lens preform from distorting in the drawing step, thus prepared optical lens can accurately act on light.
Preferably, this optical lens is an optical lens acting on light emitted from a semiconductor laser device, whereas light enters the second curved face part and exits from the first curved face part. As a consequence, the outer peripheral portion in the second curved face part, which is likely to generate distortions upon drawing, can be kept from being used as the optically active part.
It is also an object of the present invention to provide an optical lens, constituted by a pair of surfaces substantially parallel to each other and a curved face connecting the pair of faces to each other, yielding a substantially fixed cross section along a surface parallel to the pair of surfaces, the cross section being defined by a noncircular first curve, a second curve having a principle curvature smaller than that of the first curve and opposing the first curve, and third and fourth curves connecting both ends of the first and second curves to each other.
Also provided is an optical lens in which principle curvature centers of the third and fourth curves are disposed outside the above-mentioned cross section. This form exhibits a state in which parts of the third and fourth curves where neither incident light nor outgoing light transmits therethrough are slightly recessed inward.
It is also an object of the present invention to provide an optical lens, having a substantially fixed cross section in a surface orthogonal to a longitudinal direction, made by drawing and cutting an optical lens preform having a form substantially similar to the cross section, wherein curve parts corresponding to the first and second curves have respective principle curvatures greater than those of the first and second curves corresponding thereto.
Further, it is an object of the present invention to provide an optical lens, having a substantially fixed cross section in a surface orthogonal to a longitudinal direction, made by longitudinally drawing and cutting an optical lens preform having a form substantially similar to the cross section, and a cross section constituted by fifth and sixth curve parts corresponding to the first and second curves and a substantially linear part corresponding to the third and fourth curves, wherein the first and second curve parts have respective principle curvatures greater than those of the fifth and sixth curves.
Furthermore, it is an object of the present invention to provide an optical lens configured such that light enters from a surface constituted by the second curve part and exits from a surface constituted by the first curve part.
As a consequence of such a configuration, the focal length can be elongated by using such an optical lens, which can make it easier to set lenses arranged on the inner side of this optical lens.
It is also an object of the present invention to provide an optical lens preform, constituted by a translucent material, having a substantially fixed cross-sectional form along a plane orthogonal to a longitudinal direction, the cross-sectional form being defined by a noncircular first curve part, a second curve part having a principle curvature smaller than that of the first curve part and opposing the first curve part, and third and fourth line segments connecting both ends of the first and second curve parts to each other, wherein the first and second curve parts are constituted by at least a curve part having a plurality of curvatures.
Further, it is an object of the present invention to provide an optical lens preform configured such that curved parts of center portions of the first and second curve parts have respective principle curvatures greater than those of curved parts of peripheral portions thereof.